search_replace.rb

dir = "."
search = "someterm"
replace = "replace term"
extension = ".cfg"

files = Dir.new(dir).entries
files.delete(".")
files.delete("..")

files.each do |filename|
  full_path = "#{dir}/#{filename}"
  if extension.include?(File.extname(full_path))
    file = File.open(full_path, 'r')
    updated_file = ""
    file.each do |line|
      updated_file << line.gsub(/#{search}/, replace)
    end
    file.close
    file = File.open(full_path, 'w')
    file.write(updated_file)
    file.close
  end
end